Method for fluid extraction and apparatus therefor



Oct. 31, 1967 w. G. P. DOYLE ETAL 3,350,001

METHOD FOR FLUID EXTRACTION AND APPARATUS THEREFOR Original Filed Oct.20, 1964 s Sheets-Sheet 1 //Vl EN7'0RS. WLADZ/A GPODB/EL/V/AK DOYLE BYCOLL/N M. DOYLE Oct. 31, 1967 w, G. P. DOYLE ETAL 3,350,001

METHOD FOR FLUID EXTRACTION AND APPARATUS THEREFOR Original Filed Oct.20, 1964 3 Sheets-Sheet 2 1 INVENTORS. WLA DZ/A G. POOH/EL NIAK 00 YL EBY COLL/N M. DOYLE Oct. 31, 1967 w. G. P. DOYLE ETAL 3,350,001

' METHOD FOR FLUID EXTRACTION AND APPARATUS THEREFOR Original Filed Oct.20, 1964 3 Sheets-Sheet 5 DOYLE COLL/N M. DOYLE By PH-1 5 5 UnitedStates Patent ABSTRACT OF THE DISCLOSURE A method of fluid extraction inwhich at least two liquids, one a solvent and the other a solute, areintroduced at spaced apart points into an apparatus. The liquids aredispersed into droplets gradiently (in progressively increasing ordecreasing size) as the liquids move into contact with each other; and acentrifugal countercurrent exchange apparatus, for practicing saidmethod, of the indexable disc column type in which indexing rods areassociated with the rotatable discs of the disc columns. By appropriatemovement of the indexing rods, the size of the perforations of the discsmay be varied simultaneously in progressively increasing, decreasing orconstant rela tionship to each other.

This invention relates generally to a method for extracting fluids andmore particularly pertains to the extraction of fluids in a fluidextraction device whereby the droplet dispersal and mixing energycharacteristics of the fluids are varied progressively throughout thedevice. Still more particularly, the invention relates to improved disccolumns of the type described in U.S. Patent Nos. 3,132,100 and3,114,706 granted to Wladzia Gajda Podbielniak (Doyle) entitledrespectively Disc Columns for Centrifugal countercurrent ExchangeDevices and Centrifugal Countercurrent Exchange Device WithInterchangeable Disc Columns, which are readily adaptable for use whenperforming the novel method of the invention herein.

This application is a continuation of our co-pending patent applicationentitled Disc Columns in Countercurrent Exchange Devices, Ser. No.405,055, filed Oct. 20, 1964 and now abandoned.

As described in the aforementioned U.S. patents, the efficiency of anyextraction device is totally dependent upon the degree of intimatemixing of the fluids and this in turn is achieved by the dispersion ofthe fluids into droplets. Control of the character and extent of thedrop let dispersion affords a means for varying the mixing energy withinthe device. Hence, the smaller the droplets' the more intimate is thecontact between the fluids.

Recently, it was discovered that when processing two liquids in acountercurrent exchange device which have the tendency to emulsify, theemulsification could be averted if the droplet dispersal characteristicsof the liquids are varied progressively or gradiently throughout theradial length of the countercurrent exchange device. For example, inpenicillin extraction when an extractive solvent such as amyl acetate isused, theextractive solvent is fed into the outer or peripheral portionof the rotor, whereas the high potency broth or beer containing thepenicillin solute and having a greater specific gravity than theextractive solvent is fed into the rotor adjacent the periphery of therotor. When the broth is at maximum potency, there is the greatesttendency for the liquids to emulsify upon contacting each other. Hence,to prevent the emulsion in this example, the droplet dispersion of theliquids should be at the maximum adjacent the axis of the rotor. As thebroth flows outwardly toward the periphery of the rotor and contacts theextrac- 3,350,001 Patented Oct. 31, 1967 tive solvent, the potency ofthe broth decreases progressively. When the high gravity broth finallyreaches the input position of the low gravity extractive solvent, thepotency of the broth is substantially reduced from What it was when thebroth was initially introduced. At this radial level within the rotor,the fresh extractive solvent extracts the remaining penicillin solutefrom the broth. With the potency of the broth at a minimum strengthadjacent the periphery of the rotor, there is no longer the tendency ofthe liquids to emulsify. Hence, the droplet dispersion at this level maybe made minimal to afford maximum liquid contact. Therefore, since theextraction of the solute from the broth takes place progressivelythrough the rotor, the tendency of the liquids to emulsify decreases asthe broth travels toward the periphery. Consequently, the dropletdispersion could be safely decreased on a graduated or progressive basisfrom the axis to the periphery of the rotor which corresponds to theprogressive decrease in the potency of the broth.

In the case where chloroform is used as an extractive solvent, thedroplet dispersion characteristics of the exchange device should be theconverse. Since the chloroform is a higher gravity liquid than the highpotency broth orbeer, it would be introduced near the axis of the rotor,whereas the high potency broth would be introduced near the periphery ofthe rotor. As in the other example, the tendency to emulsify would begreater at the area or radial level where the high potency broth isinitially introduced, which now is adjacent the periphery of the rotor.Accordingly, to prevent the occurrence of liquid emulsion and to haveoptimum system efliciency, the droplet diepersion pattern should varyprogressively from a maximum droplet dispersion adjacent the peripheryof the rotor to a minimum droplet dispersion adjacent the axis of therotor.

Similarly in other types of liquid extraction devices; i.e., gravitycolumns, mixers and settlers, rotating disc columns, centrifuges, etc.,the same conditions would prevail.

It is therefore a primary object of this invention to provide a methodof eflicient fluid extraction. It is a related object to efficientlyextract a substance from contacting liquids without causing theemulsification of liquids when extracting the desired substancetherefrom.

It is another object to provide a method for varying the contactingsurface area between two mixed liquids in order to efiiciently extract aparticular substance therefrom and to optimize the amount of liquidswhich could be processed during a given unit of time.

It is another object to provide a method for efficiently extracting asubstance from contacting liquids within a centrifugal countercurrentexchange device.

It is still another object to optimize the efficiency of operation ofsolvent extraction devices, including countercurrent devices, bydecreasing progressively the size of the droplet dispersion tocorrespond to the decrease in the potency of the fluid from which thesolute is being extracted.

It is therefore a primary feature of this invention to provide spacedapart partition walls having apertures therein. The combined areas ofthe apertures within each Wall are made to vary progressively from thepoint of introduction of one fluid to the point of introduction of asecond fluid. The relative aperture areas determine the relativecontacting surface areas between fluids at various positions betweensaid points of fluid introduction.

In the countercurrent exchange devices described in the aforementionedpatents, removable disc columns were used to vary the droplet dispersioncharacteristic of the device by varying the perforation pattern of thedisc columns. These exchange devices comprised a rotor having spacedconcentric separator bands therein with a plurality of series of alignedholes arranged to afford cavities extending radially from the innermostto the outermost of the separator bands. The disc columns were removablypositioned in each of said cavities. In said Patent No. 3,114,706, thedroplet dispersion pattern was varied by the interchanging of the disccolumns. However, to achieve the maximum degree of adjustability andversatility in these devices, it was required to stock a great number ofcomplete disc columns and/ or a great number of individual discs ofvarying perforation patterns. The disc columns described in said PatentNo. 3,132,100 overcame this undesirable feature and comprised anelongated tie rod of polygonal cross-section having a plurality of discassemblies removably mounted thereon with each disc assembly separatedone from the other by a tubular vertical spacer removably postioned onsaid tie rod. Each disc assembly included a pair of perforatedcontiguously, superimposed discs formed with polygonal central openingsof complementary configuration to that of the polygonal cross-section ofthe tie rod, thereby enabling the same to be removably mounted on saidtie rod. The cooperation of the tie rod and central openings of thediscs for each disc assembly afforded indexing means for varying theperforation pattern of the disc assemblies by changing positions of onedisc in relation to the other disc, in order that various conditions ofdroplet dispersion could be achieved. Although these disc columns werean improvement, they nevertheless had many objectionable features. Forexample, if a variation in the perforation pattern of the disc columnwas necessary, it was required to remove the individual disc assembliesfrom the tie rod and reposition the discs of the disc assembly aroundthe tie rod. Moreover, the adjustability of the discs was limited by thenumber of sides of the polygonal configuration of the tie rodcross-section. Furthermore, these disc columns did not have thecapability to vary the perforation pattern throughout the radial lengthof the rotor on a precise graduated basis and hence these exchangedevices operated at less than optimum efficiency.

An improved disc column is disclosed in this application which overcomesthe aforementioned problems and is capable of providing in a simple andprecise manner, the desired graduated droplet dispersal patternthroughout the countercurrent exchange device. Said improved disc columngenerally comprises a plurality of disc assemblies and each of thesedisc assemblies comprises a stationary disc and a movable discselectively rotatable with relation to each other without necessitatingthe removal of the discs from the disc column. An indexing rod isassociated with each of the movable discs, which permits the rotation ofall of the discs simultaneously to achieve a uniform perforation patternor a graduated perforation pattern. In another embodiment, the discassemblies each having a movable disc with a plurality of indexingperforations that cooperate with an indexing projection on a fixed discto accomplish graduated indexing of the disc perforations.

It is therefore another primary object of this invention to provide animproved disc column for countercurrent exchange devices wherein thedisc column is completely adjustable to different perforation patternswithout requiring the removal of any discs therefrom and with but aminimum number of operations to adjust the disc column.

Still another important object of this invention is to provide animproved disc column for countercurrent exchange devices of thecharacter described wherein the movable discs thereof can be adjustedsimultaneously with one operation to achieve either a uniform or agraduated perforation pattern throughout the disc column.

Yet a further object of this invention is to provide an improved disccolumn of the character described which may be inexpensively fabricatedand yet is most efficient for the purposes intended.

With the foregoing and other objects in view, which will appear as thedescription proceeds, the invention consists of certain novel methodsand features of construction, arrangement and a combination of partshereinafter fully described, illustrated in accompanying drawings, andparticularly pointed out in the appended claims, it being understoodthat various changes in the form, proportion, size, and minor details ofstructure may be made without departing from the spirit or sacrificingany of the advantages of the invention.

For the purpose of facilitating an understanding of our invention, wehave illustrated in the accompanying drawings preferred embodiments,from an inspection of which, when considered in connection with thefollowing description, our invention, its mode of construction, assemblyand operation, and many of its advantages should be readily understoodand appreciated.

Referring to the drawings, in which like characters of reference areemployed to indicate corresponding parts throughout the several figures:

FIG. 1, is a fragmentary, vertical sectional view of a centrifugalcountercurrent exchange device with interchangeable disc columnsembodying the principles of our invention;

FIG. 2, is an enlarged vertical view of an improved disc columnembodying the principles of our invention;

FIG. 3, is a top view of FIG. 2;

FIG. 4, is a bottom view of FIG. 2;

FIG. 5, is a cross-sectional view taken on the plane of line 55 in FIG.2 and viewed in the direction indicated;

FIG. 6, is a cross-sectional view taken on the plane of line 6-6 in FIG.2 and viewed in the direction indicated;

FIG. 7, is a fragmentary view similar to FIG. 2, but with only oneindexing rod and the inner and outer disc assemblies shown 'with oneother disc assembly, said indexing rod being shown in its open position;

FIG. 8, is a cross-sectional view taken on the plane of line 8-8 in FIG.7, viewed in the direction indicated and illustrating the relationshipof the discs of a disc assembly in its open position";

FIG. 9, is a fragmentary elevational view similar to FIG. 7, wherein thedisc assemblies are shown with the indexing rod in its closed position;

FIG. 10, is a sectional view taken on the plane of line 1010 in FIG. 9,viewed in the direction indicated, and illustrating the relationship ofthe discs of a disc assembly in its closed position;

FIG. 11, is a fragmentary, elevational view similar to FIGS. 7 and 9,wherein the indexing rod thereof is torsionally positioned to afford agraduated perforation pattern in the disc assemblies;

FIG. 12, is a sectional view taken on the plane of line 12-12 in FIG. 11and viewed in the direction indicated;

FIG. 13, is a view similar to FIG. 11, wherein the indexing rod istorsionally disposed to afford a graduated perforation pattern in thedisc assembly opposite from that shown in FIG. 11;

FIG. 14, is a sectional view taken on the plane of line 1414 in FIG. 13and viewed in the direction indicated;

FIG. 15, is a plane view of a modified stationary disc to be used in adisc column without an indexing rod;

FIG. 16, is a modified movable disc to be used in superimposedrelationship with the disc of the embodiment shown in FIG. 15; and

FIG. 17, is a sectional view taken on the plane of line 17-17 in FIG.15.

Referring to the drawings, a preferred embodiment is illustrated whichmay be used when performing the method of our invention. However, aswill be more apparent as the description proceeds, other structuralarrangements may be used and are within the contemplation of theinvention. Turning now to FIG. 1, the reference numeral 10 indicatesgenerally a centrifugal countercurrent exchange device. Since the basiccountercurrent exchange device 10 is generally well known and a detaileddescription of it appears in the aforementioned US. Patent Nos.3,114,706 and 3,132,100, only so much thereof as is necessary for anunderstanding of the subject invention will be described. The devicethus comprises a shaft 12 suitably journalled for rotation in asupporting structure 14. A rotor 16 is rigidly connected to the shaft 12for rotation therewith, and the entire device may be enclosed in aremovable protective cover 17.

Suitable passageways such as 18 and 20 are provided in the shaft 12 forrespectively supplying the heavier liquid to the central area of therotor 16 and removing the lighter liquid therefrom. Similarly, suitablepassages such as 22 and 24 are provided for respectively supplying thelighter liquid under pressure to the peripheral area of the rotor 16 andremoving the heavier liquid therefrom. Communicating with the passageway24 for removing the heavier liquid may be passageways 26, providedbetween the spill-over discs 28 as indicated. The separator bands 32 maybe slightly perforated or preferably completely imperforate over theirentire areas save for a plurality of holes arranged in alignedrelationship to afford a series of disc column cavities such as 34, 36,38 and 40.

Removably positioned within each of the cavities 34, 36, 38 and 40, isone of our novel disc columns 42. The disc column 42 (see FIG. 2)comprises a central tie rod 41, which is hexagonal in cross-sectionthroughout its length except for the end portions 43, 44. The endportion 43 may include a shoulder portion 43a and a washer portion 43binterposed between the shoulder portion 43a and the disc assemblies 45.As seen in FIG. 2, the end portion 43 terminates in a polygonal shape430 that is dimensioned to be received in openings suitably drilled andpositioned in the drive shaft 12 at the inner portion of the rotor 16.The end portion 44 of each of the disc columns is associated with theouter wall of the rotor 16 as will be more fully explained hereafter.Although the cross section of the tie rod 41 is shown as beinghexagonal, other noncircular constructions of the tie rod 41 arecontemplated.

Removably mounted on the tie rod 41 is a plurality of disc assemblies 45(FIG. 2). Each of the disc assemblies 45 includes a movable disc 46 anda stationary disc 48 in contiguously superimposed relationship. Themovable discs 46 have central circular openings 50 circum-. scribing thehexagonal tie rod 41 and being sized to afford rotation therearound forthe purpose of indexing the disc assemblies 45. The stationary discs 48have hexagonal central openings 52 having the identical configuration ofthe cross-section of the tie rod 41. Thus, once the stationary discs 48are assembled with the tie rod protruding through their centralopenings, they cannot be rotated.

Each of the discs 46, 48 are preferably formed with a plurality ofperforations of varying size such as 57, 58 (FIG. 4). The size and shapeof said perforations are substantially identical in each disc assembly.The per forations 57, 58 of each disc are radially spaced from thecenter of each disc assembly 45 and are arcuately spaced equally onefrom the other around the center of each of said disc assemblies. Thus,when the disc assemblies 45 are positioned with the sets of perforations57, 58 of the movable discs 46 thereof in alignment with the sets ofperforations 57, 58 of the stationary discs, the disc assemblies are intheir open position as shown in FIG. 8. Conversely, when the movablediscs 46 are positioned so that the perforations in both discs of thedisc assembly are completely obstructed, the disc assemblies are intheir closed position, as illustrated in FIG. 10.

Our disc columns are similar to those described in US. Patent No.3,132,100 in that vertical spacers 54 are interposed between each pairof disc assemblies 45 and they are removably mounted on the tie rod 41,to provide spacing of the disc assemblies in accordance with theseparator bands 32. However, the disc assemblies 45 are retained by theshoulder portion 43a at end portion 43; and the other end portion 44 isprovided with a means for releasably locking the discs for the purposeof indexing. As will be seen from FIG. 2, a lock nut 44a cooperates withthe tie rod 41 by threadedly engaging a cap screw 44b which in turnthreadedly engages the end of the tie rod. The lock nut 44a is separatedfrom the disc assemblies 45 by a lock washer 440. Thus, when the movablediscs 46 are positioned in their desired places, the tightening of thelock nut 44a releasably locks the disc assemblies 45 in the positionsdesired. The cap screw 44b also serves as a means for adjusting thelength of the tie rod so that it can be extended within the rotorcasing.

Once the disc columns 42 are indexed and locked into position, they areoperationally retained in the rotor 16 by means of their end portions 43being positioned in the shaft 12 as seen in FIG. 1. A plurality ofcircular portholes 68 may be provided in the cylindrical outer wall oftherotor in alignment with each of the cavities 34, 36, 38 and 40. Plugs60 may be threadedly associated with each of the portholes 68 and thesame preferably abut the heads of the cap screws 44b after the length ofthe cap screws 44b have been adjusted to operationally retain each ofthe disc columns 42 within the rotor. For purposes of explanation, thedisc assemblies 45 closest to the shaft will be referred to as the innerdisc assembly; and the disc assemblies 45 closest to the outer end ofthe rotor will be called the outer disc assembly.

As seen in FIG. 5, each movable disc 46 includes openings 46a, 46b whichopen to the periphery and are diametrically opposed. A pair of indexingrods 56, 56 may be associated with the movable discs 46 by extendingthrough the aligned openings 46a, 46b in all of said movable discs ofthe disc column 42. In the preferred construction, the indexing rods 56,56 are shown fixedly attached at 56a to the movable disc of the innerdisc assembly and hence is adjacent to the shaft of the device 10 whenthe disc columns 42 are assembled in the device. The indexing rods 56,56 are removably associated with all the other openings of the movablediscs 46 of the disc assemblies 45. The indexing rods 56, 56 correspondin length to the distance between the top and the bottom movable discsof the disc column 42; and they each have an extending portionoverlapping the movable disc 46 of the outer disc assembly.

As seen in FIG. 6, each of the stationary discs 48 are formed with apair of diametrically-opposed, peripherally opening, elongated, arcuateindexing grooves 48a, 48b. The indexing rods are positionable and aremovable within said grooves. These indexing grooves 48a, 48b haveopposite end walls 48c, 48d which limit the path of movement of theindexing rods 56. It has been found that in .the case of equally spacedsets of perforations, the movement of the movable disc with relation tothe stationary disc an angular distance of one-half /2) of the number ofdegrees of spacing between the perforations, accomplishes completeindexing of the disc assemblies from an open position as illustrated inFIG. 8, to a closed position as illustrated in FIG. 10. Accordingly, inthe illustrated disc assembly where there is equal spacing of two setsof six perforations 57, 58 the angular length of the arcuate grooves48a, 48b is thirty (30) degrees. This provides complete indexingadjustability between the movable discs 46 and the stationary discs 48.From FIG. 4 it will be seen that we have shown the stationary disc inthe outer disc assembly as not having any indexing grooves because wehave found that this construction enables us to more firmly lock theindexing rods into position when the lock nut 44a is tightened. However,for description purposes, We will refer to all the stationary discs ashaving the same configuration.

There are many different indexing positions that our novel disc column42 offers. Turning now specifically to FIGS. 7 and 8 it will be seenthat when the indexing rods are rotated to their open position at oneend of the elongated arcuate indexing grooves 48a, 48b, the movablediscs 46 are caused to rotate with respect to the stationary discs 48and be positioned with their sets of perforations 57, 58 in a fullyaligned or open relationship. When the indexing rods 56 have beenrotated to their closed position at the other extreme end of theelongated arcuate indexing grooves 48a, 481), as illustrated in FIG. 9,the sets of perforations 57, 58 are fully obstructed. As seen in FIG. 2,the indexing rods 56 are shown positioned midway between the ends of theelongated arcuate indexing grooves 48a, 48b. Accordingly, the movablediscs 46 have been partially rotated with the stationary discs 48, sothat the perforations are partially obstructed asillustrated in FIG. 6.

Still another type of indexing can be achieved when the indexing rods 56are torsionally or spirally moved to the positions illustrated in FIGS.11 and 13. As shown, one extreme disc assembly 45 is in its openposition and the opposite extreme disc assembly 45 is in its closedposition. In these positions, the movable discs 46 of the disc columnare moved with relation to the stationary discs 48 on a graduated basisso that the sets of perforations 57, 58 in the discs are graduallyobstructed. Thus, in the case where the indexing rods have beentorsionally moved to the position illustrated in FIG. 11, the inner discassembly 45 is in its closed position with its perforations fullyobstructed as seen from FIG. 10. However, the outer disc assembly, whichis closest to the periphery of the rotor 16 has its perforationsunobstructed. Thus, this disc assembly is in its open position asillustrated in FIG. 8. Of course, the disc assemblies that arepositioned between the inner disc assembly and outer disc assembly arepartially obstructed on a graduated basis. Accordingly, FIG. 12 shows adisc assembly which is disposed near the outer disc assembly as beingpartially obstructed and nearly completely open. On the other hand,where the indexing rods 56 have been moved to an equal distance from theopposite end wall of indexing groove 48 position as shown in FIG. 14,the same disc assembly of FIG. 12 is substantially more obstructed andnearly closed. If the inner disc assembly of FIG. 13 were shown, itwould be fully open, whereas the outer disc assembly would be fullyclosed, because the indexing rods are in the exact opposite position tothat of FIG. 11.

In addition to torsional positioning of the indexing rods 56 with theirends either in the open or closed positions for the extreme oppositedisc assemblies as illustrated in FIGS. 11 and 13, the indexing rodscould be torsionally positioned at different angles between the twoextremes shown. Accordingly, different increments of perforationgraduation through the disc columns 42 between these two extremes offully open and fully closed may likewise be achieved.

As aforementioned, We have also provided a modified disc assembly for adisc column which is indexable without indexing rods. This modified discassembly also can be indexed without being removed from a disc columnand with a minimum number of operations. Accordingly, FIG. 15illustrates a modified stationary disc 60 having two sets of multipleperforations such as 62, 63 therein. These perforations are preferablydisposed with relation to the discs in the same positions as theaforementioned perforations 57, 58. The modified stationary discs 60have an hexagonal central opening 64, which can be assembled withrelation to a tie rod in the same manner as the discs hereinbeforementioned. An indexing projection 60a is formed in the modifiedstationary disc 60; and it is preferably located near the peripherythereof on the same diameter as one of the equally spaced sets ofperforations, 62, 63. A modified movable disc 65 having a plurality ofarcuately spaced indexing perforations 65a is provided in the modifieddisc assembly. As in the case of the other disc assemblies 45, it issuperimposed in a contiguous relationship with the modified movable disc61 so that its projecting indexing portion 60a can register with eachone of the arcuately spaced indexing perforations 65a. The modifiedmovable disc 61 also has two sets of perforations 62, 63, equally spacedtherearound. As in the case of the aforementioned movable discs 46, italso is provided with a central circular opening 66, which is seized tocircumscribe, in freely rotatable relationship, the tie rod 41 in orderto afford preselected rotational positioning of the modified movablediscs 61 with relation to the modified stationary discs 60 for indexingpurposes. The arcuately spaced indexing perforations 65a are disposedalong the length of a thirty (30") degree are which extends from thecenter diameter of one of the equally spaced sets of perforations 62,63. The thirty (30) degree are is therefore substantially the samelength as the elongated arcuate indexing grooves 48a, 4812 so thatindexing from the open to the closed positions can be realized.

Thus, it will be seen that when it is desired to index a disc columnembodying our modified disc assemblies, each of the modified movablediscs is rotated with respect to the modified stationary discs, and thearcuate indexing perforations cooperate with the projecting indexingportions to obtain different degrees of obstruction in the discassemblies in accordance With thedifferent possible indexing positions.When the modified movable discs are properly set, a locking means suchas the locking nut44a can then be used to hold the modified discs inposition.

In the foregoing, an improved disc column was disclosed which isparticularly adaptable for accomplishing the method of this invention.The novel method herein enables fluids to be processed efiicientlywhereby the amount of fluid extraction per unit of time is optimized.Moreover, the method is particularly suitable for efficiently extractingsolute from a mixture and at the same time preventing liquids which havethe tendency to emulsify from doing the same.

The novel method comprises generally, the introduction of a firstquantity of a fluid into an area and the introduction of a second fluidinto an area spaced from the area where the first fluid is introduced.The first fluid may be a mixture of fluids which includes a substance orsolute which is to be extracted therefrom. The second fluid then wouldbe an extractive fluid for extracting the substance from the firstfluid. The fluids are caused to mix together. The extraction takes placewithin the space between the areas of fluid introduction. However, thequantities of the fluids are caused to be dispersed into streams or intodroplets of progressively varying size between the areas of introductionof the fluids. The largest size streams or the minimum dispersion of thequantities of fluid are caused to occur in the area of the extract-richfluids, and hence adjacent to the area of introduction of the fluidhaving the extract substance therein. In the area of the extract-richfluids, extremely intimate contact between the fluids is not essential.Conversely, the smallest size streams or the maximum dispersion of thefluids are caused to occur in the area where the fluids have the leastamount of the extract substance therein, and hence should be adjacentthe area where the extractive fluid is introduced. In this area,extremely intimate contact between the fluid is necessary in order toextract the remaining substance within the first fluid. By progressivelyvarying the dispersion of the fluids, the effect of the extractivesolvent and the available mixing force in extracting the desiredsubstance is optimized.

This method of progressively varying'the droplet dispersion of fluidsmay also be used in any of the known types of solvent extractors, viz,rotating disc columns, mixers and settlers, centrifuges and gravitycolumns. in these types of systems, intimate contact between fluids forextracting a particular substance is achieved by the downward movementof higher specific gravity fluid and the upward movement of a lowerspecific gravity fluid. The fluids mix and a substance is extractedtherefrom as they pass through spaced apart apertured partition wallswhich define successive mixing chambers. The progressive variation ofthe size of the apertures in the partition walls correspondingly variesthe contacting surface area of the fluids within the contactingchambers.

The aforementioned method is particularly suited to the centrifugalcountercurrent exchange device 10. When the device 10 is used, a firstfluid is introduced adjacent the periphery of the rotor and a secondfluid having a greater specific gravity than the first fluid isintroduced adjacent the axis 12 of the rotor. One of the fluids is anextractive fluid and the other fluid includes a substance or solute tobe extracted therefrom. Partitions such as the bands 32 are spaced apartbetween the axis 12 and the periphery of the rotor to define a pluralityof fluid contacting chambers. Perforations are provided within each bandto permit communication between chambers. The perforation patternswithin the bands are varied progressively between the axis and theperiphery of the rotor. The largest perforation pattern which causes aminimum dispersion of the fluids is positioned adjacent the areas of theextract rich fluids. As the countercurrent exchange device operates, thefluids travel between the axis and the periphery of the rotor and thesolute is extracted progressively within the radial length of the rotor.

In the example given earlier relating to the processing of penicillin,the broth was dispersed to the greatest degree adjacent the rotorperiphery, and therefore the relative size of the droplet pattern of thebroth and solvent extraction at the rotor periphery was smaller than atany other area within the rotor. In this manner, the broth which at thisradial level contains a very small amount of solute therein, makesextremely intimate contact with the fresh extractive solvent (amylacetate), and the remaining amount of solute is thereby easilyextracted. Furthermore, at the periphery the fluids are able to utilizethe increased energy due to the circumferential rotor velocity. Thisfurther insures adequate contact between the low potency broth and thesolvent, for extracting the remaining penicillin.

The improved disc column 42 affords a precise and convenient means forproviding the desired progressive perforation patterns within the rotor.The perforation patterns of the disc assemblies 45 are variedprogressively when an upper portion of the indexing rod 56 is positionedadjacent one end wall of the indexing groove 48 in the stationary discof the outer disc assembly :and a lower portion of the indexing rod 56is positioned adjacent the opposite end wall but of the indexing groove48 in the stationary disc of the inner disc assembly. In this manner,the maximum relative perforation pattern occurs at one extreme end ofthe disc column which may be either adjacent the axis or the peripheryof the rotor, and the minimum relative perforation pattern occurs at theopposite extreme of the disc column which also may be either adjacentthe axis or the periphery of the rotor. Thus, the perforation patternsbetween the extreme end assemblies vary progressively. Therefore, as isobviously seen, the simple manipulation of the indexing rod provides thedesired perforation pattern for the entire disc column 42.

From the foregoing description and drawings, it should be apparent thatwe have provided both a novel method and a novel and improved disccolumn which fulfills the stated objects of our invention in aremarkably unobvious and unexpected fashion. As aforedescribed, the discassemblies have pairs of discs that are readily indexed to affordvariously sized perforation patterns with a minimum number of operationsand without the necessity for removing the discs from the disc columns.Also, the new and novel indexing means employs indexing rods whichenable the disc assemblies to be selectively adjusted in one operationeither when it is desired to have a uniform perforation pattern in eachof the disc assemblies, or a progressively graduated perforationpattern.

Moreover, our method disclosed herein optimizes the amount of asubstance which may be extracted from a fluid mixture in a unit of timeby progressively varying the intimate contacting area between fluids. Ameans of accomplishing this is by progressviely or gradiently varyingthe perforation patterns in the spaced apart partitioned walls which arepositioned between the areas of introduction of the two fluids whosespecific gravities vary one from the other. The disc column 42 disclosedherein is particularly suitable to precisely controlling the desiredprogressive perforation pattern throughout the disc assemblies of thedisc column.

Furthermore, our method eliminates the possibility of liquidsemulsifying when a solute is extracted from a high potency liquid. Thisis accomplished by dimensioning the perforation pattern suflicientlylarge within the areas where the fluids are rich in their content ofsolute.

Although disc columns used in centrifugal countercurrent exchangedevices have been described with great detail as providing the desiredprogressive aperture variations, other means for achieving the same arewithin the contemplation of the invention. Moreover, the method may bepracticed in means other than centrifugal contactors, such as, forexample, gravity columns having spaced apertured decks, mixing andsettling tanks, rotating disc columns, etc.

It should be realized that while we have illustrated and described ourinvention with relation to a pair of straight indexing rods, otherindexing rods of different shapes can be embodied in this invention whenit is desired to vary the patterns on a different basis other thanlinearly. Also, it is not necessary to have a pair of indexing rods andindexing grooves to accommodate said indexing rods, as our disc columnscould operate with merely one indexing rod and with indexing grooves toaccommodate merely one indexing rod.

Still further, it is believed that our invention, its mode ofconstruction and assembly, and many of its advantages should be readilyunderstood from the foregoing without further description, and it shouldalso be manifest that while a preferred embodiment of the invention hasbeen shown and described for illustrative purposes, the structuraldetails are nevertheless capable of wide variation within the purview ofour invention as defined in the appended claims.

What we claim and desire to secure by Letters Patent of the UnitedStates is:

1. In a centrifugal countercurrent exchange device including -a rotor, ashaft, a plurality of spaced concentric bands having holes formedtherein to aflorda radially extending cavity, a disc column positionedin said cavity, said disc column comprising:

an elongated tie rod;

a plurality of disc assemblies removably mounted in spaced relationshipon said tie rod, each of said disc assemblies including a movableperforated disc and a stationary perforated disc, said discs beingcontiguously superposed on each other;

indexing means to enable the movable discs of said disc assemblies to berotated in place about said tie rod and thereby vary the indexing of theperforations of said movable disc in relation with the perforations ofsaid stationary disc for the corresponding disc assembly; and

locking means to prevent said stationary disc from rotating while themovable disc of the corresponding disc assembly is being rotated aboutthe tie rod.

2. In a centrifugal countercurrent exchange device as claimed in claim1, wherein:

said tie rod has a non-circular cross-section shape and;

said stationary disc includes a non-circular central openingcomplementary to the non-circular crosssectional shape of said tie rod,said locking means comprising the cooperation of the non-circular tierod and the complementary non-circular central opening of saidstationary disc; and

said indexing means comprises rotating means cooperating with a circularcentral opening formed in said movable discs, said circular openingbeing dimensioned to accommodate said tie rod therethrough and to permitthe rotation of said movable discs about said tie rod, said rotatingmeans being associated with each of said movable discs and capable ofsimultaneously rotating said movable discs through progressively varyingarcuate distances about the tie rod, thereby providing a progressivevariation of the perforation patterns through said disc assemblies.

3. In a centrifugal countercurrent exchange device as claimed in claim2, wherein said rotating means comprises:

an elongated arcuate indexing groove formed in the stationary discs ofsaid disc assemblies;

a notch formed in each of the movable discs to accommodate said indexingrod; and

at least one indexing rod extending through said indexing grooves andthrough said notches to link said disc assemblies together, saidindexing grooves having end walls to limit the movement of said indexingrod, the movement of said indexing rod within said indexing groovescausing only the mov able discs to rotate about said tie rod as theindexing rod applies force against the edges of the notches of themovable discs.

4. A countercurrent exchange device as claimed in claim 3, wherein themovable disc and the stationary disc for each assembly have identicalsets of perforations therein, the perforations of each of said sets areradially spaced from the center of the disc assembly, said sets ofperforations are separated from each other by an equal number ofdegrees, the arcuate length of said arcuate indexing groovescorresponding to one half /2) of said degree separation between saidsets of perforations, said arcuate length of said grooves permittingsaid indexing rod to vary the openings through said disc assemblybetween a maximum open position when the indexing rod is positioned atone end of the groove to a fully closed position when the indexing rodis positioned at the other end of said arcuate groove.

5. A countercurrent exchange device as claimed in claim 4, wherein atleast one indexing groove of each stationary disc is in alignment withan indexing groove of each of the other stationary discs, thepositioning of said indexing rod through said aligned indexing grooveswhereby an upper portion of the indexing rod is adjacent one end wall ofthe arcuate indexing groove of the stationary disc of one of said endassemblies and a lower portion of the indexing rod is adjacent theopposite end Wall of the arcuate indexing groove of the opposite enddisc assembly provides a progressively varying perforation patternthrough said disc column from one of said end disc assemblies to theother of said end disc assemblies, said progressively varyingperforation pattern causing the intimate fluid contact-ing area tocorrespondingly vary in a progressive manner.

6. A countercurrent exchange device as defined in claim 5, wherein:

the upper end of said indexing rod is fixedly attached to the movabledisc of the outer upper end disc assembly;

the stationary disc of said lower end disc assembly does not have anindexing groove to receive said indexing rod and thereby serves toprotect the lower end of the indexing rod from being moved out of place;and

a closure means threadedly associated with said tie rod to maintain saiddisc assemblies securely in place when tightly abutting against saidlower stationary disc.

7. A countercurrent exchange device, as claimed in claim 1, wherein eachof said movable discs is formed with a plurality of indexingperforations disposed at an equal distance radially around the centerthereof, each of said stationary discs having an integrally formedproject-ing index portion protruding outwardly therefrom and being sizedand disposed to be received by any of said indexing perforations in saidmovable discs, whereby said movable disc of each disc assembly can berotatably indexed with relation to each of said stationary discs in aplurality of fixed positions by moving the disc with the indexingperforations to alignment of one of the preselected perforations withthe projecting indexing portion of the stationary disc of thecorresponding disc assembly.

8. A countercurrent exchange device, as claimed in claim 7, wherein saiddiscs of each disc assembly are of the same size and have identical setsof perforations therein, and each set of said perforations are radiallyspaced from the center of said disc assemblies and are arcuately spacedapart equally one from the other about the center of said discassemblies.

9. A countercurrent exchange device, as claimed in claim 8, wherein saidindexing perforations and projections are disposed near the peripheriesof said discs, and said indexing perforations are disposed within an areequal in length to half of the degree spacing between said sets ofperforations, said indexing perforations being located with respect toeach of said indexing projections to enable said movable discs to beindexed to fixed posit-ions within said are between an open perforationposition and a closed perforation position.

10. A method of fluid extraction comprising:

introducing a quantity of an extractive solvent fluid into a first area;

introducing a quantity of a fluid having a substance to be extractedtherefrom into a second area spaced from the are-a of introduction ofsaid solvent fluid;

moving said fluids towards each other; and

causing said quantities of fluids to be dispersed gradiently betweensaid points of introduction of said fluids to vary gradiently the areaof intimate contact of said fluids between said areas of introduction,the minimum'dispersion of said fluids occuring adjacent the area ofintroduction of the quantity of said fluid having said substance to beextracted therefrom.

11. A method of fluid extraction as claimed in claim 10, wherein thegradient dispersal of said fluids is caused by moving said fluidsthrough spaced apart perforations of progressively variable size betweenthe areas of introduction of the fluids, the larger of said perforationsacting as a conduit means for extract-rich fluids.

12. A method of fluid extraction as claimed in claim 10, wherein saidfluids are liquids and perforated spaced apart partition walls arepositioned between the areas of introduction of said liquids, the areasof the perforations of the partition walls varying gradiently from theinnermost to the outermost partition wall, the gradient dispersal ofsaid fluids is caused by passing said liquids through the perforationsof said partition walls whereby the largest area of said perforations iswithin the partition wall adjacent the point of introduction of theliquid having said substance therein.

13. A disc column for countercurrent exchange devices comprising:

holding means;

a plurality of disc assemblies mounted in spaced relationship andmaintained in position by said holding means, each of said discassemblies including a movable perforated disc and a stationaryperforated disc, said discs being superposed one on the other; and

indexing means capable of simultaneously rotating all of said movablediscs with respect to said sta- References Cited tionary discs of thecorresponding disc assemblies UNITED STATES PATENTS through arcuatepaths the length of which vary from movable disc to movable disc,thereby provid- 5633307 7/1896 .Paulus 137 625-31 X ing gradientvariation of the perforation patterns 5 1 through said disc assemblies.

14. The disc column of claim 13 wherein said indexg g 3 1 137 625'3 Xing means comprises at least one indexing rod associated gig ig g ggl il i with each of said movable discs, said indexing rod being 0 1e maoperatively movable in a path other than about its own 10 HENRYKLlNKslEKPrimary Examineraxis to cause rotation of said movable discs.M. CARY NELSON, Examiner.

1. IN A CENTRIFUGAL COUNTERCURRENT EXCHANGE DEVICE INCLUDING A ROTOR, ASHAFT, A PLURALITY OF SPACED CONCENTRIC BANDS HAVING HOLES FORMEDTHEREIN TO AFFORD A RADIALLY EXTENDING CAVITY, A DISC COLUMN POSITIONEDIN SAID CAVITY, SAID DISC COLUMN COMPRISING: AN ELONGATED TIE ROD; APLURALITY OF DISC ASSEMBLIES REMOVABLY MOUNTED IN SPACED RELATIONSHIP ONSAID TIE ROD, EACH OF SAID DISC ASSEMBLIES INCLUDING A MOVABLEPERFORATED DISC AND A STATIONARY PERFORATED DISC, SAID DISCS BEINGCONTIGUOUSLY SUPERPOSED ON EACH OTHER; INDEXING MEANS TO ENABLE THEMOVABLE DISCS OF SAID DISC ASSEMBLIES TO BE ROTATED IN PLACE ABOUT SAIDTIE ROD AND THEREBY VARY THE INDEXING OF THE PERFORATIONS OF SAIDMOVABLE DISC IN RELATION WITH THE PERFORATIONS OF SAID STATIONARY DISCFOR THE CORRESPONDING DISC ASSEMBLY; AND